云南格咱岛弧印支期斑岩型铜矿床变化与保存研究

Geza arc located in the southern tip of the Yidun island-arc belt which is an important geological parts of the “Sanjiang” volcanic-magmatic belts in northwestern China. Its formation began at the Ganzi-Litang oceanic crust westward subduction in the Late Triassic, which experienced intracontinental convergence and post-orogenic extensional phase in Yanshanian and showed a strong thrust-nappe structure and large-scale strike-slip translation activities affected by the collision uplift of the Qinghai-Tibet Plateau in the Himalayan. In this area, there were strong magmatism and superior metallogenic geological conditions. It was a newly discovered copper polymetallic ore concentration area of China in the recent years, where the Pulang porphyry copper deposit is a typical representative of the Indosinian porphyry copper deposits. This application on the basis of previous studies, using the biotite TAl geobarometer and Apatite Fission Track (AFT) method restore the uplift and erosion history of granitic rocks in the Geza arc and got the denudation quantitative data of intrusions to research on the evolution of deposits post-ore changes and preservation. According to the quantitative calculation and classification of erosion resources to typical porphyry deposits, which can provided the theory basises for evaluation of the metallogenic potential and the deep prospecting of porphyry metallogenic system.

格咱岛弧带是西南“三江”古特提斯阶段形成的一个重要的地质构造单元，位于扬子西缘义敦岛弧带南段。它始于晚三叠世甘孜-理塘洋壳的向西俯冲，燕山期经历了陆内汇聚和造山后伸展作用阶段，喜山期受青藏高原碰撞隆起效应的影响，表现为强烈的逆冲-推覆构造和大规模走滑平移。区内岩浆活动强烈，成矿地质条件优越，是近年来新发现的重要铜多金属成矿带，其中以印支期产出于普朗复式岩体的斑岩型铜矿最为典型。本申请在前人研究基础上，利用黑云母TAl地质压力计和磷灰石裂变径迹（AFT）法获取岩体剥蚀程度和剥蚀速率的定量数据，通过斑岩体形成深度与剥蚀程度的对比研究，分析区内矿床形成后变化与保存情况，探索格咱岛弧花岗质杂岩体的隆升-剥蚀历史。根据区内典型矿床剥蚀资源量的计算和分级，以期为斑岩成矿系统资源潜力评价和深部找矿提供理论依据。

格咱岛弧位于西南三江构造火成岩带义敦岛弧南端，是晚三叠世甘孜—理塘洋壳向德格—中甸陆块俯冲的产物，是我国近年来新发现的重要铜多金属成矿带。该区强烈的构造—岩浆活动贯穿于岛弧造山作用的始终，丰富的成矿作用发育于岛弧造山的不同时代、不同环境。在以往研究基础上，本项目采用黑云母TAl压力计获得格咱岛弧成矿带典型成矿岩体的固结压力变化于0.25～1.53kbar，岩浆侵位深度为0.84～3.85km，表明格咱岛弧成矿斑岩体具有明显的浅成侵位的特点。低温热年代学的研究表明，格咱岛弧成矿带内主要成矿岩体的磷灰石裂变径迹年龄分布12±1～68±5Ma。结合成岩成矿的同位素年龄，揭示了区内主要斑岩型铜矿床含矿岩体的岩浆侵入作用与冷却过程的时限，限定了斑岩型铜矿成矿作用的时代与剥露历史。通过岩体的剥蚀程度与铜多金属矿床的形成深度来分析，各成矿岩体的剥蚀深度都小于侵位深度，这对矿床形成后的保存较为有利。根据区内主要斑岩型矿床剥蚀资源量的定量计算，将矿床剥蚀情况划分为3个数量级，为斑岩成矿系统资源潜力评价和深部找矿提供了理论依据。